Venting structure for battery grid mold



United States Patent 1132111; l64/372all, 4l0all, 305all, Battery Digest;

18/Venting Digest; 22/Battery Digest [56] References Cited UNITED STATES PATENTS 1,717,608 6/1929 Kadow ..1.64/Battery Digest Primary ExaminerJ. Spencer Overholser Assistant Examiner-V. K. Rising Attorney-Barnes, Kisselle, Raisch and Choate ABSTRACT: A battery grid mold having a vent bar set into a channel extending across the mold face. The edges of the bar contacting the sides of the channel being relieved at spaced points to provide vent passageways sufficiently large to permit venting of air therethrough but sufficiently small to prevent the flow of molten metal into said passageways. The rear side of the channel communicating with a passageway in the mold leading to a port at the edge of the mold for exhausting air through the vent passageways or for supplying pressurized air to the vent passageway when the mold face is being sprayed with a mold coat.

VENTING STRUCTURE FOR BATTERY GRID MOLD This invention relates to molds for casting a battery grid and more specifically to a venting construction for such molds.

Battery grid molds normally comprise two separable mold sections on the mold faces of which grooves are machined to correspond with the pattern of the battery grid. The grid pattern essentially comprises a plurality of vertical and horizontal wires (the ribs which form the open mesh network of the grid) surrounded by a frame portion. Such battery grids frequently vary in thickness from between .050 inches to .060 inches. It is apparent, therefore, that the cavity defined by the juxtaposed grooves of the closed mold sections is of relatively small cross section. Normally such molds are arranged so that the battery grid cast therein is vertically disposed and the cavity is filled by pouring the molten metal composition downwardly into an inlet trough extending across the upper end of the mold. It has been common practice in the past to provide a slightly recessed face portion adjacent the lower end of one of the mold halves to permit venting of air downwardly out of the bottom of the mold as the molten metal flows downwardly through the grooves. A bottom ventofthis type is very desirable but experience has shown that the provision of such bottom vent does not itself assure the avoidance of entrapment of air in the upper portions of the grid. If air is trapped in grooves forming the grid pattern, the wires of the grid are imperfectly formed (that is, they are'discontinuous); and an unsatisfactory grid is produced.

It has been proposed heretofore to vent such molds above the bottom portion thereof by forming small holes through the mold so that the holes emerge at the mold face at the flat rectangular face portions between the grooves forming the grid wires. Such holes are expensive to form; they provide imperfect venting and frequently become plugged with molten metal. It has also been proposed to avoid the problems encountered with such vent holes by making the holes of larger diameter and inserting pin-s in the holes having portions ground flat so as to provide a clearance between the pin and the hole of a size large enough to vent air buy not sufficiently large to admit molten metal. Such venting not only is expensive but also does not assure the casting of consistently perfect grids.

The primary object of this invention is to provide a venting structure for battery grid molds which is of economical manufacture and which assures the casting of consistently perfect grids.

More specifically the invention has for its object the provision of a venting structure for a battery grid mold in the form of a channel in the mold face of one of the mold sections with a vent bar in the channel. The vent bar is machined to form with the sides of the channel regularly spaced vent passageways which communicate with an exhaust passageway extending to a port at the edge of the mold, the port being adapted to be connected with a source of pressurized air or to discharge to the surrounding atmosphere so that when the battery grid is being cast, air is permitted to escape through the vent passageways on the vent bar and out of the mold through the exhaust passageway and when the' mold face is being sprayed with a mold coat, pressurized air can be directed through the vent passageways to prevent them from becoming sealed with the mold coat,

Other features and advantages of the present invention will become apparent from the following description and drawing, in which:

FIG. I is an elevational view of a battery grid mold section provided with the venting structure of the present invention.

FIG. 2 is a sectional view of a pair of closed mold sections provided with the venting structure of the present invention and taken generally in the plane ofline 22 in FIG. 1.

FIG. 3 is a fragmentary view, on an enlarged scale, of the rear side of the vent bar.

FIG. -l is a sectional view of a pair of closed mold sections taken substantially in the plane ofline 4-4 in FIG. 1.

In FIG. I one ofa pair of complementary battery grid mold sections is illustrated and designated 10. The other complementary mold section is illustrated in FIG. 2 and designated 12. The mold sections 10 and 12 are suitably mounted on a battery grid casting machine so that they are separable to ma ble removal of the cast battery grid after casting. Since the present invention is concerned solely with the venting structure on the mold and not with the manner in which the molds are supported for relative movement toward and away from one another, such supporting structure is not illustrated. Likewise, the means for ejecting the cast grid from the mold is not illustrated.

The mold face 14 illustrated in FIG. 1 has a plurality of grooves machined therein which define the grid pattern. The shape of the grid and the arrangement of the wires (that is, the ribs of the grid) will vary from one battery grid to another. However, the pattern in general comprises a plurality of vertical grooves 16 which are intersected by a plurality of horizontal grooves 18 which define the wires ofthe grid. This grooved grid pattern is normally surrounded by peripheral grooves 20 at each side and along the top and bottom which define the periphery of the battery grid. The flat rectangular face portions 21 form the open spaces between wires of the cast grid. The cavity in the mold may also include a pair of grooves 22 spaced below the lower peripheral grooves 20 which, when filled with molten metal, form a chill bar. In addition, the cavities may be provided as indicated at 24 and 26 for forming lugs on the battery grid as cast.

At the upper end of the mold the two mold sections are formed with inclined recesses 28 which, when the mold sections are closed, define a V-shaped inlet trough 30, the lower edge ofwhich communicates with flat recessed portions 32 on each mold section which form the sprue portion of the grid casting. As is conventional, after a battery grid is cast it is trimmed along its upper and lower edges to remove the sprue portion formed in the recesses 32 and the lugs formed by the recesses 24 together with the chill bars and any flash adjacent thereto. In the mold illustrated two interconnected battery grids are adapted to be cast simultaneously and eventually sheared and trimmed into separate grids.

When casting a battery grid in a mold generally of the type illustrated a molten lead composition is poured into the trough 30 which flows downwardly to fill the grooves 16, 13 and 20.

In order to obtain complete filling of the mold grooves it is es-- sential that the air in these grooves be vented. Along their lower edges the mold sections 10 and I2. are recessed slightly below the chill bars 22 as indicated at 34 to vent air from the lower end ofthe mold along this section of the mold. The molten metal will solidify as a flash on the cast grid at the bottom vent 34 of the mold. Experience has shown that the provision of a bottom vent such as shown at 34 is not sufficient to completely vent the mold and result in complete filling of the grooves in the 'mold, particularly the fine grooves l6 and 18. As the level of the molten metal rises in the cavities formed by grooves 16, 18 and 20, the air in these grooves above the molten metal must be vented; if it becomes trapped a discontinuity will result in the grid formation.

In order to permit the escape of air from adjacent the upper end of the mold, one of the mold sections (the section designated 10 in the drawing) is formed with a rcctangularlyshaped channel 36 of the mold face 14 thereof. Channel 36 extends entirely across the grid pattern as illustrated in FIG. 1. Behind the channel 36 mold section 10 is formed with a passageway 38 which extends entirely across the mold section and terminates at opposite ends in ports 40 and 42. Port 42 is plugged while port 40 is adapted for connection with a hose 44 or the like which extends to a source of air under pressure. Preferably a suitable quick-disconnect coupling 46 is provided for attaching hose 44 to port 40. Passageway 38 is located generally at the level of channel 36. The bottom wall of channel 36 is formed with a pair of elongated ports 48 which establish free communication between channel 36 and passageway 38.

Within channel 36 there is arranged a vent bar 50. Vent bar 50 is retained within channel 36 by means of three screws 52 which extend through mold section 10 from the back side thereof and thread into vent bar 50. Thefront or exposed face of vent bar 50 is flush with mold face 14 and the grid pattern of grooves l6, l8 and 20 is extended into and across the front face of vent bar 50. The upper, lower and rear faces of vent bar 50 are ground as shown in FIG. 3 to provide flat, shallow recesses 54 around these three sides of the bar. These recesses define pads 56 spaced along the length of bar 50 which have a close fit with the side walls and the bottom wall of channel 36. In the drawing the recesses 54 are illustrated on a highly exaggerated scale for purposes of illustration. In actual practice recesses 54 have a depth of only about .0015 inches to .002 inches. Recesses 54 provide vent passageways 57 extending from the mold face 14 of mold section 10 through ports 48 and into passageway 38. The cross-sectional width of vent passageways 57 formed by recesses 54 is sufficiently large to permit air to pass freely therethrough but are sufficiently small to prevent the ingress ofmolten metal.

To further assist in venting the mold, the mold face of mold section I is undercut slightly throughout a major portion thereof within the lateral side edges of the grid pattern. In FIG.

1 the undercut portion of mold face 14 extends from the line 58 adjacent the left side of the grid pattern to the broken line 60 adjacent the right side of the grid pattern. This undercut or face vent (designated 62 in FIG. 4) is obtained by simply grinding the mold face between the lines 58 and 60 to a depth of about .0015 inches. The face vent 62 on mold section further facilitates the venting of air upwardly in the mold cavity particularly between the juxtaposed rectangularly shaped flat surface portions Zl bounded by grooves 16, 18 and 20.

In casting battery grids with the mold structure shown herein a predetermined amount of molten metal is poured into trough 30. The rnetal flows downwardly primarily through the wider side grooves 20 to the bottom of the cavity defined by grooves grid pattern. The metal flows downwardly beyond the lower grooves 2 into the bottom vent portion 34 and into the chill bar grooves 22. The metal flowing into the vent portion 34 solidifies as a flash and the level of the molten metal rises progressively throughout the grooves defining the grid cavity. As the level of metal rises it displaces the air above it. This is facilitated by the face vent 62 on mold section 10 provided between lines 58 and 60. The air that is displaced upwardly in the grid cavity is discharged through the vent passageways 57 defined by recesses 54, through ports 43 and out of the mold through passageway 38. While grids are being cast, hose 44 is disconnected from port 40 so that passageway 33 discharges to atmosphere.

Periodically it is necessary to spray the faces of mold sections it) and I2 with a mold coat (not illustrated). When the from channel 36 the entire channel becomes exposed for cleaning, and with the vent bar removed the latter may be cleaned by wire brushing or the like to remove any foreign metal that might become lodged in the vent passageways.

Iclaim:

1. A mold for casting battery grids comprising a pair of separable mold sections, one of said mold sections having a mold face provided with a plurality of grooves therein which when the mold sections are closed define a cavity which corresponds at least in part to the grid to be cast, said cavity having an inlet at its upper end for molten metal to enable filling of the cavity, said mold face having a channeltherein extending transversely .thereacross, a passageway within said mold section located behind said mold face and communicating with said channel, said passageway extending to a port at an edge portion of said one mold section, a vent bar in said channel, said vent bar having edge portions fitting closely with and against the sides of said channel and having other edge portioris at said mold face spaced from the sides of the channel to define vent passageways extending from said mold face to said first-mentioned passageway, said vent passageways being of a size to permit the passage of air therethrough but to prevent ingress of molten casting metal therein whereby said port may be connected to a source of pressurized gas when a mold coat is applied to'said mold face of said mold section to prevent said vent passageways from being plugged with the mold coat and when the cavity is being filled with molten metal to cast a battery grid the air displaced by said molten metal is permitted to escape from the mold through said vent passageways and out of the mold through said port.

2. A battery grid mold as called for in claim l wherein said channel and vent bar extend horizontally across said mold face adjacent the upper end of the grooved grid pattern therein.

3. A battery grid mold as called for in claim 1 wherein said channel and vent bar extend completely across the grooved grid pattern on said mold face.

4. A battery grid mold as called for in claim 1 wherein said vent passageways have an effective thickness of not more than about .002 inches.

5. A battery grid mold as called for in claim 1 wherein said channel is formed with upper and lower side faces which extend in generally parallel planes perpendicular to the plane of said mold face.

6. A battery grid mold as called for in claim 5 wherein the vent bar is formed with upper and lower parallel faces which fit closely with the upper and lower faces of said channel, said vent passageway s'being defined by recesses in said upper and lower faces of the vent bar.

mold coat is being applied hose 44 is connected to port 40 to direct pressurized air outwardly through vent passageways 57 and thereby prevent these vent passageways from being sealed with mold coat.

The venting structure described herein has several distinct advantages over venting arrangements previously employed. In addition to the fact that this venting structure assures complete filling of the mold cavity, it is also desirable from the standpoint of manufacture and mold maintenance. The grinding of channel 36 and vent bar 50 is considerably less expensive than forming accurately sized small holes and pins in the face of the mold. In addition. the particular vent structure disclosed enables the mold face 14 to be sprayed with a mold coat such as a liquid cork composition without the danger of the vent passageways becoming sealed or clogged. This is accomplished by merely directing air under pressure from hose 44 through the vent passageways 57 while the mold face is being sprayed. Furthermore, in the event that the vent passageways do become clogged with mold coat, dirt or the like, it is a simple matter to retract screws 52 and remove vent bar 50 from within channel 36. With the vent bar removed 7. A battery grid mold as called for in claim 6 wherein the front face of the vent bar is substantially flush with said mold face.

3. A battery grid mold as called for in claim "7 wherein said grooved grid pattern extends across the front face of said vent bar.

9. A battery grid mold as called for in claim i wherein said first-mentionedpassageway communicates with the bottom of the channel.

10. A battery grid mold as called for in claim 1 wherein said mold face is recessed slightly from a vertical lines spaced laterally inward of and adjacent one side edge of the grid pan tern therein to a second vertical line spaced laterally inward of and adjacent the opposite side edge of the grid pattern therein.

11. A battery grid mold as called for in claim 1 wherein said channel is of generally rectangular shape in vertical cross section and said vent bar is correspondingly shaped, said other edge portions of said vent bar comprising longitudinally spaced recesses extending along the upper, lower and back sides of the vent bar.

12. A battery grid mold as called for in claim ll wherein said first-mentioned passageway extends longitudinally of and communicates with the bottom of the channel. 

